1. Field of the Invention
This invention relates to an oscillator usable in various apparatuses such as mobile radio communication equipments.
2. Description of the Prior Art
A good way of miniaturizing an oscillator is to form at least part of the oscillator by an integrated circuit (IC).
Japanese published unexamined patent application 64-8704 discloses an oscillator designed to be formed by an IC. In the oscillator of Japanese patent application 64-8704, a power supply voltage is directly applied to the collectors of transistors, so that the amplitude of an oscillator output vibrates around the power supply voltage and an RF oscillator signal tends to leak toward the power supply. In addition, since the power supply voltage is directly applied to the bases of the transistors, the base bias voltages can not be freely set to optimal values which are determined from the standpoint of a C/N ratio (a carrier-to-noise ratio). Furthermore, the base voltages and the collector voltages fluctuate with variations in the power supply voltage, so that the C/N ratio tends to be lowered by the variations in the power supply voltage.